The present invention relates to a magnetic recording system, and, particularly to a magnetic recording system provided with double-layered perpendicular media having a soft magnetic under layer and a single pole type write head.
To advance the high recording density of a magnetic disk drive, a double-layered perpendicular recording system is considered advantageous in which double-layered perpendicular media having a recording layer and a soft magnetic under layer, and a magnetic head which mounts a single pole type write head are combined. The single pole type write head is provided with a main-pole, a return-pole, and a coil for generating a write field applied from the main-pole to the double-layered perpendicular media. Moreover, the single pole type write head is usually fabricated in one body together with a read head which arranges a magneto-resistive effect element between a pair of regenerated shields. The double-layered perpendicular media have the soft magnetic under layer, the recording layer, and a protective layer formed on a substrate. Also in some cases, the double-layered perpendicular media may insert a non-magnetic layer between the recording layer and the soft magnetic under layer, or between the soft magnetic under layer and the substrate for the purpose of improving the crystalline of the upper layer and film adhesion. As an applicable composition, the single pole type write head provides a soft-magnetic material in the vicinity of the main-pole to change recording field distribution. In this description, a magnetic pole for generating a magnetic field in which magnetization is finally formed on the recording medium is defined as the main-pole.
In a conventional longitudinal magnetic recording system, data is written to the medium using the magnetic field leaked from a write head gap. On one hand, in the case of using the double-layered perpendicular media, because a magnetic flux generated from a recording element flows into the soft magnetic under layer, the recording field applied to the recording layer increases, and this characteristic is an advantage for high density. On the other hand, when a magnetic field is applied from the outside of the drive, as shown in FIG. 14, the magnetic flux concentrates on the magnetic head/soft magnetic under layer, and there is the possibility of an extremely large magnetic field being generated in comparison with an externally applied magnetic field, directly under the main-pole of the magnetic head. When a stray field concentrates on the magnetic head in this manner, the erasure of recorded data or the deterioration of signal quality occurs. There is the possibility of this problem being reduced due to the structure/magnetic property of the magnetic head and the structure/magnetic property of the soft magnetic under layer. However, because a double-layered perpendicular recording system is more sensitive to an external field than the conventional longitudinal magnetic recording system, this problem cannot be prevented theoretically in the double-layered perpendicular recording system.
To prevent this problem, it is proposed heretofore that a soft magnetic shield is added to the entirety or a part of the drive. Even in either case, the object is to bypass the magnetic flux by the external field via the shield by adding the shield, and reduce the magnetic flux flowing into the head and recording medium inside the drive. The shield in this case uses the outside of the drive or, at least, the outside of the head and the entirety of the medium as a circumventing path of the magnetic flux.